How Flyway works

It will try to
locate its metadata table. As the database is empty, Flyway won't find it and will
create it instead.

You now have a database with a single empty table called SCHEMA_VERSION
by default:

This table will be used to track the state of the database.

Immediately afterwards Flyway will begin scanning the filesystem or the classpath of the
application for migrations.
They can be written in either Sql or Java.

The migrations are then sorted based on their version number and applied in
order:

As each
migration gets applied, the metadata table is updated accordingly:

schema_version

installed_rank

version

description

type

script

checksum

installed_by

installed_on

execution_time

success

1

1

Initial Setup

SQL

V1__Initial_Setup.sql

1996767037

axel

2016-02-04 22:23:00.0

546

true

2

2

First Changes

SQL

V2__First_Changes.sql

1279644856

axel

2016-02-06 09:18:00.0

127

true

With the metadata and the initial state in place, we can now talk about migrating to newer
versions.

Flyway will once again scan the filesystem or the classpath of the application for migrations. The migrations are
checked against
the metadata table. If their version number is lower or equal to the one of the version marked as current, they
are ignored.

The remaining migrations are the pending migrations: available,
but not applied.

They are then sorted by version number and executed in order:

The metadata table is updated accordingly:

schema_version

installed_rank

version

description

type

script

checksum

installed_by

installed_on

execution_time

success

1

1

Initial Setup

SQL

V1__Initial_Setup.sql

1996767037

axel

2016-02-04 22:23:00.0

546

true

2

2

First Changes

SQL

V2__First_Changes.sql

1279644856

axel

2016-02-06 09:18:00.0

127

true

3

2.1

Refactoring

JDBC

V2_1__Refactoring

axel

2016-02-10 17:45:05.4

251

true

And that's it! Every time the need to evolve the database arises, whether structure (DDL)
or reference data (DML),
simply create a new migration with a version number higher than the current one. The next time Flyway starts, it
will
find it and upgrade the database accordingly.